Regarding an electronic apparatus such as a portable radio and a headphone apparatus, there has been an apparatus that incorporates winding means winding and retracting an input cord and passage cord of headphones, in which these cords are energized by the force of a spring so as to be wound and retracted inside, locking means for locking only at the time of winding is provided, the cords are pulled out with necessary lengths against the locking means when the earphones or headphones are used, and the cords are wound by the force of the spring at the time of storage, with a release button which releases the locking means being pushed.
Cord-winding means used for the above described headphone apparatus has been disclosed in Patent Literature 1. FIG. 8 shows the whole structure of a headphone apparatus disclosed in the above-described Patent Literature 1, and FIG. 9 is a cross-sectional view of FIG. 8 shown by the A-A line. In FIG. 8, regarding left and right headphone housings 1L and 1R, shell-like front and rear housings 2a and 2b constitute a casing as shown in FIG. 9, in which a drive unit (hereinafter referred to as D/U) 3 of such as a loudspeaker, which is an electro-acoustic transducer, is attached to the front housing 2a, a sound hole la which radiates acoustic pressure generated from the D/U is provided in the front surface of the front housing 2a, and an ear pad 4 is provided on the front surface of the front housing 2a. 
Normally, a headphone apparatus is worn on the left and right ears, so that, as shown in FIG. 8, an input cord 9 extending from an input plug 8 having a connection terminal 8a connected to an electronic apparatus is pulled into one casing, for example, into the left headphone housing 1L and is connected to the D/U 3 in the left headphone housing 1L. A lead wire 10 is a passage cord to be pulled into the right headphone housing 1R and is connected to the D/U 3 in the right headphone housing 1R. On the passage cord 10 is slidably held a slider 11 for adjusting freely the length of the passage cord 10 when folded. Further, a protruding portion 2c constituting holding means is formed on the left and right headphone housings 1L and 1R. An insertion opening 2d into which the input plug 8 can be inserted is provided in the protruding portion 2c. 
When winding and retracting the input cord 9 with the input plug 8 being held by the insertion opening 2d of the protruding portion 2c constituting holding means, locking means which locks and prevents the input cord 9 from being wound and retracted by later-described winding means energizing to wind and retract the cord into the left headphone housing 1L is released, and thus the input cord 9 is wound and retracted by the winding means, however, since the input plug 8 has been held by the protruding portion 2c of the holding means in advance, the input plug 8 is not pulled in along with the input cord 9, and the input plug is therefore prevented from hitting the human body at the time of winding. In addition, reference numerals 4, 5 and 7 in FIG. 8 are an ear pad, a supporting portion and an ear hook respectively, which are described later on.
Next, the internal structure of the left and right headphone housings 1L and 1R is explained referring to FIGS. 9 to 11. FIG. 9 is a side sectional view of a headphone housing portion that incorporates winding means, FIG. 10 is an enlarged sectional view of the portion B in FIG. 9, and FIG. 11 is a plan view in which the internal structure of cord-winding means is seen.
The internal structure of a headphone apparatus is explained referring to FIG. 9 as follows: a pair of spindle portions 5 is provided in the vicinity of the rear housing 2b (refer to FIGS. 8 and 9), a spindle 5a protrudes from inside the spindle portions 5, a coiled spring 6 is put around the spindle 5a, and the spindle 5a is energized by the coiled spring 6 such that an end 7a of the ear hook 7 fitted into a spindle hole of the spindle portions 5 to be able to turn freely will always be energized toward the front housing 2a. The ear hook 7 has a pressed portion 7b on the opposite side to the end 7a with respect to the spindle 5a, a slip stopper 7c is provided in the pressed portion 7b, and by pressing the part with the fingers, the end 7a of the ear hook 7 moves apart from the front housing 2a. 
As regards winding means, a board 12 made of metal or the like is fixed with a plurality of screws or the like to the front housing 2a of the left headphone housing 1L into which the input cord 9 is pulled. One end of a rotating shaft 13 functioning as a pivot stands at the center of the board 12; a reel 14 is inserted and fitted into the rotating shaft 13 in a freely rotatable manner; a spring 15, both ends of which are fixed between the reel 14 and the rotating shaft 13, is accommodated in a hollow 14a of the reel 14; and the spring 15 is pressed by a pressing board 16 so as not to jump out, and is prevented from detaching by means of a C ring 13a from above the pressing board 16 at the other end of the rotating shaft 13. A plurality of protrusions 12b are provided on the lower surface of a lower flange 14d of the reel 14 to reduce friction by point-contacting the board 12 when the reel 14 rotates.
As shown in FIG. 9 and FIG. 10 that is an enlarged view of the portion B in FIG. 9, ends of an L-channel lead wire 9a, a ground (G) common lead wire 9b and an R-channel lead wire 9c, which are cords in the input cord 9 wound and retracted onto the reel 14, are electrically connected to brush-like contact points 18a, 18b, 18c, made of resilient metal boards, respectively, in a bored portion 14b formed between the board 12 and the hub of the reel 14, and the brush-like contact points 18a, 18b, 18c are concentrically installed in the bored portion 14b. On the other hand, on a terminal board 17 attached to the board 12 are provided metal slip rings 19a, 19b, 19c which correspond to the brush-like contact points 18a, 18b, 18c, constituting a commutator mechanism such that the contact points 18a, 18b, 18c are pressed to be contacted.
Therefore, when the reel 14 rotates, a sound signal input through the input cord 9 is transmitted to the terminal board 17 without being interrupted by contact and sliding between the brush-like contact points 18a, 18b, 18c, made of resilient metal boards, and the metal slip rings 19a, 19b, 19c, and then is transmitted from the terminal board 17 to terminals 3b, 3c of a terminal board 3a through lead wires 17a, 17b. Among the lead wires in the input cord 9, the common lead wire 9b and the R-channel lead wire 9c are connected to the right headphone housing 1R on the other side through lead wires 17c, 17d electrically connected with these lead wires 9b, 9c, and through the passage cord 10 which combines the lead wires 17c and 17d together.
Further, regarding locking means, the outer circumference of the lower flange 14d on the board 12 side in the two flanges of the reel 14 is divided by n to form repeatedly saw-like recesses and projections, thus constituting a plurality of ratchet wheels 14c as shown in FIG. 11. A shaft 20 is planted in an upright position in a protruding piece 12c of the board 12, and an approximately T-shaped locking piece 21 is attached to the shaft 20 in a freely turnable manner. Regarding the locking piece 21, an operational portion 21a, with which the end of the connection terminal 8a of the input plug 8 is brought in contact, protrudes; a locking portion 21b is provided at a position where the ratchet wheels 14c on the periphery of the lower flange 14d of the reel 14 is in contact; and is energized in the counterclockwise direction C in FIG. 11 by a spring 22 provided between a hooking portion 21c and a hooking portion 12d of the board 12, and therefore the locking portion 21b is always pressed to be in contact with the ratchet wheels 14c formed on the periphery of the lower flange 14d. 
Further, regarding holding means, in the protruding portion 2c of the rear housing 2b is provided an insertion opening 2d from which the connection terminal 8a of the input plug 8 is inserted, and a small diameter portion in the vicinity of the end thereof can be held by a protruding portion of a holding spring board 23.
As regards conductive state in a commutator mechanism including the above-described brush-like contact points 18a, 18b, 18c and metal slip rings 19a, 19b, 19c, in order to retain conductivity without interruption with respect to rotation movement for which durability against repeated actions is required, the brush-like contact points 18a, 18b, 18c need to be accurately assembled, however, from a structural viewpoint, there have been difficulties in production with the above-described structure. Specifically, as in FIGS. 12A to 12C showing a similar structure to FIG. 10, in order for a reel 14 to wind and store an input cord 9 as much as possible in a limited space, a space for a bored portion 14b used for providing brush-like contact points 18a, 18b, 18c is extremely limited, and so it has been necessary for the bored portion 14b having small area provided at the lower end of the hub of the reel 14 to have minimal values regarding both the thickness T and diameter D thereof. Accordingly, there has been a problem in which the thickness of the reel 14 is reduced as thin as possible as shown in FIGS. 12A to 12C, and the area of a distance D1 (refer to FIG. 12B) of a terminal pedestal 25 for the brush-like contact points 18a, 18b, 18c welded to the inside of the bored portion 14b is tiny.
Further, with a structure in which the brush-like contact points 18a, 18b, 18c are fixed to the bored portion 14b formed at the lower end of the hub of the reel 14 and the metal slip rings 19a, 19b, 19c are provided on the terminal board 17 side of the board 12 fixed to the front housing 2a or rear housing 2b, not only a jig 27 for inserting a welding pin 26 provided in an upright position on the terminal pedestal 25 into a through-hole made in the brush-like contact points 18a, 18b, 18c, and a jig 27a for welding the brush-like contact points 18a, 18b, 18c to the welding pin 26 are required in the small-area bored portion 14b as shown in FIGS. 12A to 12C, but also with the jig 27 for exclusive use, adjustment is complicated in heat-welding the metal brush-like contact points 18a, 18b, 18c to the thin terminal pedestal 25 and slight dispersion in the tiny installation area may result in defects in production.
Patent Literature 1: Japanese Published Patent Application No. 2002-10369 (FIG. 1)